There are a series of rows of stationary vanes and rotating blades in a turbine section of a gas turbine engine. In one known turbine section, the blades are coupled to a solid rotor. For each row of blades, the rotor comprises a series of circumferentially spaced apart steeples, wherein adjacent steeples define a groove for receiving a root of a corresponding blade. Hot working gases travel to the rows of blades. As the working gases expand through the turbine section, the working gases cause the blades and, hence, the rotor to rotate.
It is known to measure the depth of a third row of rotor grooves so as to determine any creep which may have occurred in the adjacent steeples. Hence, if the depth of the groove has increased, this is indicative of creep, which may limit the life of the rotor. To measure the depth of each third row groove, a measuring tool has been used that takes a single measurement within the groove. Since it is desirable to make two axially spaced apart measurements along a groove, the tool has to be removed, reversed and re-inserted after each measurement. Hence, for each groove, the tool has to be handled twice.